Micro-fluid ejection heads for micro-fluid ejection devices such as ink jet printers continue to be improved as the technology for making the ejection heads continues to advance. New techniques are constantly being developed to provide low cost, highly reliable micro-fluid ejection head structures that can be manufactured in high yield with a relatively low amount of spoilage or ejection head damage.
In order to increase ejection head speed and volume output, larger ejection heads having an increased number of ejection actuators are being developed. However, as the ejection head size and number of ejection actuators increases, manufacturing apparatus and techniques are required to meet increased tolerance demands for such ejection heads. Slight variations in tolerances of parts may have a significant impact on the operation and yield of suitable ejection head products.
The primary components of the micro-fluid ejection head are a substrate or chip containing fluid ejector actuators, and a nozzle plate and a flexible circuit attached to the chip. The chip is typically made of silicon and contains various passivation layers, conductive metal layers, resistive layers, insulative layers and protective layers deposited on a device surface thereof. For thermal micro-fluid ejection heads, individual heaters are defined in the resistive layers and each heater resistor corresponds to a nozzle hole in the nozzle plate for heating and ejecting fluid from the ejection head toward a target media. In a top-shooter type ejection head, nozzle plates are attached to the chips and there are fluid chambers and fluid feed channels for directing fluid to each of the heaters on the chip either formed in the nozzle plate material or in a separate thick film layer. In a center feed design for a top-shooter type ejection head, fluid is supplied to the channels and chambers from a slot or via that is conventionally formed by chemically etching or grit blasting through the thickness of the chip. The chip, nozzle plate and flexible circuit assembly is typically bonded to a thermoplastic body using a heat curable and/or radiation curable adhesive to provide a micro-fluid ejection head structure.
Attaching the chips to the body and curing the adhesive is a delicate procedure and may result in chip cracking and thus product yield loss. As the size of the chips increase, the difficulty associated with handling the chips without damage or breakage also increases. Larger chips require even more care when attaching the chips to a thermoplastic body so as to minimize chip cracking and warpage.
It is believed that a predominant contributor of chip warpage is the coefficient of thermal expansion mismatch between the chip and the thermoplastic body. During manufacturing, when the chip and body go through the adhesive cure cycle, chip warpage is introduced as the components cool. If the displacement for the chip from a planar configuration is too large, the chip cracks. Accordingly, there continues to be a need for improved manufacturing processes and techniques which provide improved ejection head components and structures without product loss due to chip cracking.
With regard to the above, there is provided a micro-fluid ejection head assembly having improved assembly characteristics and methods of manufacturing a micro-fluid ejection head assembly. The micro-fluid ejection head includes a fluid supply body having at least one fluid supply port in a recessed area therein. A reinforcing member circumscribes the fluid supply port. A micro-fluid ejection head is attached with an adhesive to the supply body in the recessed area so that cracking of the ejection head during adhesive curing is substantially reduced.
In another embodiment, there is provided a method for improving micro-fluid ejection assembly yield. The method includes providing a fluid supply body having a fluid supply port in a recessed area thereof therein and a reinforcing member circumscribing the fluid supply port. A micro-fluid ejection head is adhesively attached to the fluid supply body in the recessed area. The method may provide a substantially improved yield of usable micro-fluid ejection assemblies.
An advantage of the foregoing structure and method therefor is that chip warpage and thus chip cracking may be substantially reduced without the need to select materials having similar coefficients of thermal expansion. The structures and methods provided herein may be used with a wide variety of thermoplastic body materials and chip substrate materials to reduce warpage of the chip substrate during adhesive curing cycles. A wider variety of stiffener materials may be used with the thermoplastic bodies to maintain substantially lower chip warpage as compared to materials selected for a coefficient of thermal expansion that is similar to the coefficient of thermal expansion of the chip material